Known dry-cleaning processes consist of a wash, rinse, and draining/drying cycle with solvent recovery. During the dry-cleaning process, items, such as garments, are loaded into a basket disposed within a vessel and immersed in a dry-cleaning solvent that is pumped into the vessel from a base tank. Conventional dry-cleaning solvents include perchloroethylene (PCE), petroleum-based or Stoddard solvents, CFC-113, and 1,1,1-trichloroethane, all of which are generally aided by a detergent.
The use of these conventional solvents, however, poses a number of health and safety risks as well as being environmentally hazardous. For example, halogenated solvents are known to be environmentally unfriendly, and at least one of these solvents, PCE, is a suspected carcinogen. Known petroleum-based solvents are flammable and can contribute to the production of smog. Accordingly, dry-cleaning systems which utilize dense phase fluids, such as liquid carbon dioxide, as a cleaning medium have been developed. An apparatus and method for employing liquid carbon dioxide as the dry-cleaning solvent is disclosed in U.S. Pat. No. 5,467,492, entitled "Dry-Cleaning Garments Using Liquid Carbon Dioxide Under Agitation As Cleaning Medium". A similar dry-cleaning apparatus is also disclosed in U.S. Pat. Nos. 5,651,276.
These liquified gas dry-cleaning systems pose a number of other problems, particularly in relation to the high operating pressures necessary for maintaining the gas in a liquid state. Specifically, the cleaning vessel in a liquid carbon dioxide system operates at between 700-850 psi under ambient temperature conditions. In addition to the cleaning vessel, the dry-cleaning apparatus has other vessels or chambers associated with the regular operation and maintenance of the system which are regularly exposed to elevated pressures.
Following each wash cycle, for example, a wash bath liquid is cycled through a lint filter which separates lint and other coarse particulate matter from the wash bath. Because of the high operating pressures, the lint filter must have a relatively bulky, heavy-walled construction, which is costly and requires dedicated piping and high pressure seals. Moreover, since the lint filter must be accessed on a regular basis for routine cleaning and maintenance, sometimes as frequent as after the completion of each laundry load, it is desirable that the lint filter be readily accessible to an operator. However, because of the bulky construction, the access doors to such pressurized lint filter vessels can be cumbersome to open and handle. These difficulties can make it inconvenient for an operator to open the lint filter, and can discourage the operator from checking and cleaning the lint filter as frequently as is needed to ensure optimal operation of the dry-cleaning system. Since such lint filters typically have relatively small filter surface areas through which the wash bath is directed, even minor neglect in cleaning of the filter of course particulate matter can seriously impede operation of the dry-cleaning system.